Patent GB-804242-A (GB)
Title: Improvements in the production of refractory carbides, borides and the like
Inventor: AMSTEIN EDMUND HOLLIS
IPC: C01B31/30
Filed: 1954-03-05
Abstract: <PICT:0804242/III/1> In preparing refractory carbides, borides, borocarbides and mixed borides and carbides of titanium, zirconium, niobium and tantalum, or boron carbide itself by intimately mixing an oxide or oxides of titanium, zirconium, niobium, tantalum, or boron with carbon, and when the mixture does not already contain the oxide of boron and the end product is to contain combined boron, with boron or its oxide, and heating the reaction mass to a selected temperature in the range 2000-3000 DEG  C., a product of low free carbon content is ensured by (a) removing gaseous and volatile products from the reaction mass while still at a high temperature at which no substantial decomposition of CO to form free carbon can occur, and (b) by cooling the mass substantially immediately after it has reached equilibrium at the selected temperature.  Pure mineral rutile or precipitated titanium dioxide, and pure coke are ball-milled together, e.g. in a rubber-lined ball mill with carbide balls.  20-25 per cent by weight of pitch or cane sugar molasses may be used as binder.  Where pitch is used the mixture is ball milled, extruded as a rod, which is cut into cylinders, and the cylinders calcined at 1000 DEG  C. in a non-oxidizing atmosphere.  Where molasses is used, the intimate mixture is extruded and cut into cylinders, which are dried in an air oven at 100-110 DEG  C., and calcined at 1000 DEG  C. The reaction mixture may include 1 per cent alumina equivalent to the free carbon expected in the product.  Where oxide of boron is present in the reaction mixture, magnesia or other oxide, which combines with or dissolves in boron oxide may be added, to economise boron oxide, in amount equal thereto.  Where magnesia is added additional carbon may be added to react therewith.  Besides the reaction of titanium dioxide with carbon to form carbide, the Specification also refers to the preparation of titanium boride from titanium dioxide, carbon, and boron or boron oxide, and to the preparation of boron carbide from boron oxide and carbon.  The calcined cylinders at 50-100 DEG  C. are continuously fed through apertured rubber diaphragm 16, forming a gas seal, into tube 15, and thence to graphite tube 2.  Tube 2 is disposed axially in a graphite resistance element 3 in the form of a tube slit longitudinally, and the whole is axially located in graphite tube 10.  Lowvoltage current for heating is fed by watercooled terminal blocks 7, 8 to element 3.  Tube 10 is secured in casing 9 by insulated bush 14 having water-cooling element 12. Casing 9 is filled with carbon black heat-insulating material 21. Gases and volatile products at above 1500 DEG  C. are vented through aperture 2a in tube 2, aperture in tube 10 and vertical graphite outlet tube 17 surrounded by graphite tube 18, so that no decomposition of carbon monoxide to carbon dioxide and carbon occurs. Sight tubes register with apertures 32 in tube 10 to determine the temperature in tube 2. The heated cylinders pass from tube 2 into coaxial graphite quench tube 4, surrounded by copper tube 23 secured in casing 9 by bushing 24 and intensively cooled by water circulating in copper coil 25.  The cooled cylinders pass from 4 into container 31 secured by gas-tight joint 30 to hood 26, and enclosed in water-filled tank 28.  The cylinders are removed in container 31, when required, by sealing the entry to hood 26 by closure device on slidable rod 29.  Alternatively, the reaction mixture, e.g. to form borides, may be fed to the furnace in graphite boats or saggers.ALSO:In preparing refractory carbides, borides, borocarbides, and mixed borides and carbides of titanium, zirconium, niobium, and tantalum, or boron carbide itself by intimately mixing an oxide or oxides of titanium, zirconium, niobium, tantalum, or boron with carbon, and when the mixture does not already contain the oxide of boron and the end product is to contain combined boron, with boron or its oxide, and heating the reaction mass to a selected temperature in the range 2000-3000 DEG C., a product of low free carbon content is ensured by (a) removing gaseous and volatile products from the reaction mass while still at a high temperature at which no substantial decomposition of CO to form free carbon can occur, and (b) cooling the mass substantially immediately after it has reached equilibrium at the selected temperature. Pure mineral rutile or precipitated titanium dioxide, and pure coke are ball-milled together, e.g., in a rubber-lined ball mill with carbide balls. 20-25 per cent. by weight of pitch or cane sugar molasses may be used as binder.  Where pitch is used the mixture is ball-milled, extruded as a rod, which is cut into cylinders, and the cylinders calcined at 1000 DEG C. in a non-oxidising atmosphere.  Where molasses is used, the intimate mixture is extruded and cut into cylinders, which are dried in an air oven at 100-110 DEG C., and calcined at 1000 DEG C. The reaction mixture may include 1 per cent. alumina equivalent to the free carbon expected in the product.  Where oxide of boron is present in the reaction mixture, magnesia or other oxide, which combines with or dissolves in boron oxide may be added, to economise boron oxide, in amount equal thereto.  Where magnesia is added additional carbon may be added to react therewith.